Method of attaching a fastener to a plurality of panels

ABSTRACT

A method of riveting a plurality of panels utilizing a fastener which may then be used to attach a further element to the panel assembly and wherein the fastener is first permanently attached to a first panel for a later attachment to a second or plurality of panels to form the fastener and panel assembly. The fastener is attached to the first panel by piercing a tubular barrel portion through the panel and affixing the first panel in an annular groove in a flange portion surrounding the barrel portion. The groove includes radial ribs preventing rotation of the fastener in the first panel and a radial rib is deformed in an outer surface of the barrel portion preventing pull-out of the fastener. The second and further panels are pre-pierced with a conical lip surrounding the panel opening and received on the barrel portion of the fastener with the conical lip facing the first panel. An annular recess is formed in the first panel which recedes the conical lip of the second panel and the free end of the barrel portion is deformed over the second panel, flattening the conical lip radially inwardly against the barrel portion, forming a secure mechanical interlock between the fastener and the panel assembly.

RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 08/241,206 filed May 11, 1994, now U.S. Pat. No.5,423,645, which application was a divisional application of Ser. No.08/101,920, filed Aug. 4, 1993, now U.S. Pat. No. 5,335,411, whichapplication was a continuation application of Ser. No. 07/786,204, filedOct. 31, 1991, now U.S. Pat. No. 5,251,370. This application also claimspriority to German Application No. P4410475.8, filed Mar. 25, 1994.

FIELD OF THE INVENTION

This invention relates to an improved fastener and panel assembly,wherein the fastener is permanently attached to a plurality of panelsretained in face-to-face relation and the fastener may then be utilizedto retain a structural element to the panel assembly. The method of thisinvention is particularly adapted for mass production applications, suchas automotive applications, requiring intimate contact between thepanels, which may be relatively heavy gauge steel panels, and thefastener may be self-piercing and clinching.

BACKGROUND OF THE INVENTION

Self-attaching fasteners are now used extensively in mass productionapplications by the automotive and appliance industries, for example, topermanently attach a structural element to a panel, such as a metalbracket, frame member or body panel. U.S. Pat. Nos. 2,707,322 and3,648,747 disclose pierce nuts which have been widely accepted by theautomotive industry, wherein the pierce nut is permanently attached to ametal panel in a die press, and the press may also be utilized to formthe metal panel into a contoured shape. A pierce nut is permanentlyinstalled in the metal panel with each stroke of the press, wherein thepilot portion of the pierce nut pierces a slug from the panel and thepanel is then deformed into grooves provided in the body portion of thenut. U.S. Pat. Nos. 4,555,838 and 4,610,072 disclose improved fasteningsystems for permanently installing male and female fasteners in a panelin mass production applications. A fastener in such fastening systemsinclude a tubular or annular barrel portion which is riveted to thepanel during the installation. The tubular barrel portion may beutilized to pierce a slug from the panel, which is received in thetubular barrel portion as disclosed in U.S. Pat. No. 4,555,838, or apunch may be utilized to pre-pierce or simultaneously pierce the panelas disclosed, for example, in U.S. Pat. Nos. 4,711,021, 4,831,698 and4,713,872. In recent years, the automotive industry, for example, hassubstantially reduced the weight of vehicles to improve fuel efficiencyand the thickness of the metal panels and plates utilized by thisindustry has also been reduced. These fastener systems were designed, inpart, to attach a fastener to thinner panels, including steel panelshaving a thickness of about 0.030 inches.

There is a need, however, for a fastener system for heavier gauge panelsand fastener systems having improved torque resistance. The fastenersystem disclosed in the above-referenced co-pending application may beutilized with a broader range of panel thicknesses, including steelpanels ranging in thickness from 0.75 mm to 4 mm.

There is also a need for a fastener system which attaches a plurality ofpanels in face-to-face relation which has not been met by the fastenersystems disclosed in the above-referenced patents. At present, steelpanel assemblies are typically attached by spot welding. A weld fasteneris attached to one of the panels, forming a fastener and panel assembly.For example, the axle housing of an automobile may be attached to aU-shaped frame assembly which comprises two nested steel panels whichare spot welded together. Holes are formed in the panels where thefasteners are required to attach the axle assembly to the frame and thefasteners are welded to the inside panel aligned with the holes. Theframe assembly may then be dip coated with wax to reduce corrosion;however, the liquid wax wicks between the panels because the panels arenot in intimate contact. When bolts are threaded into the weld nutsattached to one of the panels, the panels are compressed and the wax isextruded from between the panels. However, because the wax is viscous,it is extruded slowly and the bolts must be tightened several times toensure a tight connection. Further, the welded fasteners may also besubject to failure under high torque loads.

The fastener and panel assembly of this invention may be utilized toattach a plurality of panels in intimate matting face-to-face relationsuch that wax, for example, will not wick between the panels and thefastener provides improved torque resistance. Further, the fastener isself-piercing, such that the fastener may be utilized in mass productionapplications in a die press. The method of this invention may also beused to interconnect two or more panels together in a conventual diepress and provides improved pull-out and push-through resistance. Thus,the fastener and panel assembly of this invention provides importantadvantages over the prior art and fulfills a need which is not met bythe present fastener assemblies.

SUMMARY OF THE INVENTION

The fastener and panel assembly of this invention includes a pluralityof plastically deformable panels permanently retained in face-to-facerelation and a fastener for attachment of other elements to the panelassembly. The fastener includes a barrel portion, preferably a tubularportion, which may be utilized to pierce an opening in the first panel,as described below in regard to the method of this invention. Thefastener further includes a flange portion which extends radially fromthe barrel portion, generally perpendicular to the barrel portion, and afastener portion generally opposite the barrel portion. Where thefastener is a female or nut-type fastener, the fastener may include athreaded bore which is coaxially aligned with the barrel portion or asmooth bore which receives a self-tapping or thread-rolling screw orbolt. Where the fastener is a male fastener, such as a stud or boltfastener, the fastener portion extends from the flange portion coaxiallyaligned with the barrel portion. In the most preferred embodiments, theflange portion includes a groove adjacent the barrel portion whichsurrounds the barrel portion to provide a mechanical interlock betweenthe fastener and the first panel.

The fastener and panel assembly of this invention further includes afirst panel having an opening which receives the fastener barrel portionand the first panel bears against the fastener flange portion and ispreferably deformed in the flange portion groove to retain the fastenerto the first panel. In the most preferred embodiment, the outer surfaceof the barrel portion includes a radial annular rib spaced from the freeend of the barrel portion which bears against the first panel,entrapping the first panel in the annular groove in the flange portion.As described below in regard to the method of this invention, theannular rib is preferably deformed from the barrel portion as thefastener is affixed to the first panel.

The fastener and panel assembly further includes a second panel havingan opening which receives the barrel portion therethrough and the freeend of the barrel portion is deformed radially outwardly over the secondpanel, permanently attaching the panels together in face-to-facerelation with the fastener portion extending from the first panel toattach another element to the panel assembly, as described above. In themost preferred embodiment, the first panel includes an annular groove orrecess which surrounds the barrel portion which is formed into the firstpanel as the panel is deformed into the annular groove of the flangeportion of the fastener. The second and further panels are then deformedinto the annular recess in the first panel, forming an intimateface-to-face contact between the panels secured by the fastener. Thefree end of the barrel portion is preferably deformed radially outwardlyinto an arcuate hook-shape over an edge of the second panel surroundingthe second panel opening and the second panel is deformed radiallyinwardly against the barrel portion forming a very secure mechanicalinterlock between the fastener and the second panel.

The preferred method of attaching a plurality of panels together inface-to-face relation with a fastener of this invention includeslocating a fastener opposite a first panel with the free end of thebarrel portion facing the first panel. The method then includes drivingthe fastener barrel portion free end against the first panel, piercingan opening in the first panel, then driving the fastener barrel portionthrough the opening in the first panel and securing the fastener to thefirst panel. The method further includes forming an opening in a secondpanel configured to receive the barrel portion of the fastener, thenlocating the second panel on the first panel in face-to-face relationwith the fastener barrel portion extending substantially through thesecond panel opening and finally deforming the fastener barrel portionradially outwardly to securely rivet the second panel to the first paneland mechanically affix the fastener to the panel assembly with thefastener extending from the first panel to attach further elements tothe panel assembly. Two or more panels may be attached to the firstpanel by the method of this invention.

In many applications, it is preferable to securely retain the fastenerto the first panel prior to receipt and securement of the second andfurther panels. In a mass production application, for example, thefastener may be attached to the first panel at one location, such aswhere the first panel is deformed into a configured shape. The fastenerand first panel assembly is then moved to a second station where thefastener and first panel assembly is attached to a second panel. In massproduction applications, the fastener and first panel assembly may beloaded into a bin with other assemblies and the fastener may becomedislodged from the first panel unless the fastener is securely retainedto the first panel. Further, as described above, the fastener may besubjected to torque loads in the panel assembly and thus the fastenermust be provided with anti-rotation means in such applications. Thus, asdescribed above, the fastener preferably includes an annular groove inthe flange portion adjacent the barrel portion which surrounds thebarrel portion. In the most preferred embodiment, the groove isgenerally V-shaped, extending radially inwardly toward the barrelportion and the groove includes a plurality of radial ribs whichgenerally bridge the V-shaped groove. The method of this invention thenincludes deforming the first panel adjacent the panel opening into theannular groove in the flange portion forming a mechanical interlockbetween the first panel and the fastener, wherein the ribs preventrotation of the fastener in the panel assembly. Further, an annularrecess is preferably deformed in the first panel as the panel isdeformed into the annular groove in the barrel portion and the secondpanel is deformed into the annular recess in the first panel, forming anintimate face-to-face relation between the first and second panels,preventing entry of foreign material between the panels, including thewax coating which may be applied to the panel assembly.

In a preferred method of this invention, the second panel is deformed inthe assembly process, preferably as the opening is formed in the secondpanel, by forming a generally conical or frusto-conical lip surroundingthe opening in the second panel having a free circular edge spaced fromthe plane of the second panel. The method then includes locating thesecond panel on the first panel with the frusto-conical lip bearingagainst the first panel. The method then includes flattening the conicallip radially inwardly against the barrel portion of the fastener as thefree end of the barrel portion is deformed radially outwardly topermanently secure the panel assembly. If additional panels are attachedover the second panel, the additional panels are preferably deformed toprovide a frusto-conical lip surrounding the panel opening, asdescribed.

Where two or more panels are attached by the fastener, the panels may bepierced and formed simultaneously. The panels are preferably retained inface-to-face relation, such as by spot welding, then pierced anddeformed adjacent the pierced opening to form a frusto-conical lipsurrounding the opening in both panels. The fastener barrel portion isthen located in the pierced panel opening with the frusto-conical lipfacing the radial flange. The frusto-conical lip is then driven againstthe first panel, flattening the conical lip of the panels, deforming thelips radially inwardly against the exterior surface of the barrel andthe free end of the barrel is simultaneously deformed radially outwardlyover the last panel, forming a secure mechanical interlock between thefastener and panel assembly.

The barrel portion of the most preferred embodiment of the fastenerincludes a first portion having a diameter adjacent the free end of thebarrel portion which is less than a second larger diameter portionadjacent the flange portion, defining a radial shoulder at the junctionbetween the first and second portions. The antirotation ribs may extendfrom the groove into the second larger diameter portion, providingimproved torque resistance for the fastener and panel assembly. Themethod of this invention then includes driving the barrel portionthrough the panel opening to receive the second larger diameter portionof the barrel portion in the panel opening. Where the panel opening ispierced by the barrel portion, the barrel portion preferably includes anouter edge which pierces an opening in the panel having a diametergenerally equal to the first smaller diameter portion of the barrelportion. Where the panel is prepierced, the diameter of the panelopening is preferably less than the diameter of the second largerportion of the barrel portion. The radial shoulder is then deformedradially outwardly forming a radial rib against the first panel,entrapping the first panel in the groove or recess in the flangeportion. Thus, the fastener is securely retained on the first panelprior to receipt of the second panel, which is desirable in massproduction applications for the reasons set forth above.

The fastener and panel assembly and method of this invention will bemore fully understood from the following description of the preferredembodiments, appended claims and drawings, a brief description of whichis set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an end perspective view of an improved female fastener whichmay be utilized in the fastener and panel assembly and method of thisinvention;

FIG. 2 is a side partially cross-sectioned view of the female fastenershown in FIG. 1;

FIG. 3 is a side partially cross-sectioned view of the fastener shown inFIGS. 1 and 2 as the fastener is being installed in a first panel in adie press;

FIG. 4 is a side partially cross-sectioned view of the fastener andfirst panel assembly in a die press, similar to FIG. 3, afterinstallation of the fastener in a first panel;

FIG. 5 is a side partially cross-sectioned side view of a die pressassembly which may be used to form the second panel;

FIG. 6 is an enlarged side partially cross-sectioned view of the diepress shown in FIG. 5 following piercing and forming of the secondpanel;

FIG. 7 is a partial side cross-sectional view of the opening formed inthe second panel;

FIG. 8 is an exploded partially cross-sectioned side view of the firstpanel and fastener assembly show in FIG. 4 in a die assembly attaching asecond panel formed as shown in FIGS. 5 and 6;

FIG. 9 is a partially cross-sectioned side view similar to FIG. 8following installation of the fastener to the second panel;

FIG. 10 is a side view of a typical installation of the fastener andpanel assembly of this invention during attachment of a further element;and

FIG. 11 is an enlarged side partially cross-sectioned view of thefastener and panel assembly shown in FIG. 10;

FIG. 12 is a side, partially cross-sectioned view, similar to FIG. 6,illustrating piercing and forming a plurality of panels in nestedrelation;

FIG. 13 is an enlarged view of the formed opening in the panels shown inFIG. 12; and

FIG. 14 is a side, partially cross-sectioned view, of a fastener andpanel assembly, wherein the panels formed as shown in FIGS. 12 and 13are attached to the fastener and the first panel assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 and 2 illustrate a preferred embodiment of a fastener 20 whichmay be utilized in the fastener and panel assembly and method ofinstallation of this invention in the form of a female fastener. Thefastener 20 includes a barrel portion 22, which is preferably annular ortubular, a radial flange portion 24 adjacent the barrel portion 22,which extends generally perpendicular to the barrel portion, and afastener portion 26 generally opposite the barrel portion 22. In apreferred embodiment, the free end 28 of the barrel portion isself-piercing, which is particularly advantageous in many massproduction applications. In this preferred embodiment of the method ofthis invention, the radial outer edge 30 of the free end 28 of thebarrel portion 22 is relatively sharp, as best show in FIG. 2, to piercea slug from the panel having an inside diameter generally equal to theoutside diameter 32 of the free end of the barrel portion as describedbelow in regard to the method of this invention. Further, the outsidediameter of the barrel portion at 32 adjacent the free end 28 is smallerthan the outside diameter at 34 adjacent the flange portion 24 defininga radial shoulder 36, as best show in FIG. 1. Thus, as the barrelportion is driven into the opening pierced by the smaller diameterbarrel portion 32 the larger diameter portion 34 provides aninterference fit with the hole in the first panel, as described below.

The flange portion 24 includes an outer annular panel bearing surface 38and an annular groove 40 adjacent the barrel portion 22 and surroundingthe barrel portion. As best show in FIG. 2, the groove 40 is V-shapedhaving a bottom wall extending radially into the bearing surface 38 ofthe flange portion toward the barrel portion and an inside wallcoincident with the outer surface 34 of the barrel portion. In thepreferred embodiment, the groove includes a plurality of spaced radialribs 42 which extend from the groove into the surface 34 of the largerdiameter barrel portion, providing excellent torque resistance of thefastener in the panel assembly.

As described above, the disclosed embodiment of the fastener 20 is afemale fastener having an internally threaded bore 44 which ispreferably coaxially aligned with the internal surface 46 of the barrelportion. Where the female fastener is used with a self-tapping or threadrolling screw or bolt, the bore 44 will be unthreaded. Further, asdescribed above, the fastener 20 may be a male fastener, wherein thefastener portion 26 may be solid and the free end may be threaded, forexample, to provide a bolt fastener in the fastener and panel assemblyof this invention. In the disclosed embodiment, the female fastenerportion 26 includes a tubular portion 48 and a sealing cap or slug 50which is retained in a slot 52 in the free end 54 of the tubular portion48 and the free end 54 is deformed or coined over the cap 52 as shown inFIG. 2. A sealing cap 50 is provided in applications where foreignmaterial must be kept out of the fastener assembly, such as automotiveapplications where the panel and fastener assembly is coated or wherethe fastener assembly is subjected to oil, dirt and road debris.

FIGS. 3 and 4 illustrate the installation of the fastener 20 in a firstpanel 58. In a typical application, the panel 58 is steel, such as lowcarbon, 1010 steel or high strength, low alloy steel (HSLA), and thefastener 20 is formed of a harder steel, such that the barrel portion 22will pierce the steel panel 58. A suitable material for the fastener isa 35 carbon steel with boron, such as a 10 B35 or 35B2 wherein the nutmay be heat treated to Class 10. The fastener 20 may be installed in adie press and the panel 58 may be preloaded by a conventional stripperplate (not shown). In the installation shown in FIGS. 3 and 4, thefastener 20 is received in a fastener installation head in the upper dieshoe of a die press (not shown), which includes a reciprocating plunger60 which bears against the driven surface 56 of the flange portion 24. Afemale die member or die button 62 is located in the lower die shoeassembly (not shown) and the free end 28 of the barrel portion 22 isdriven against the first panel 58 by the plunger 60, as shown by arrows64. The die button 62 includes a bore 66 which receives the panel slugand an annular spanking lip 68 which deforms the panel into the groove40 as described below in regard to FIG. 4. The die button 62 furtherincludes a relatively sharp piercing edge 70 adjacent the bore 66 whichcooperates with the piercing edge 30 of the barrel portion 22 to piercea slug from the panel, as now described.

In the method of this invention, the fastener 20 is first located by theinstallation head with the free end 28 of the barrel portion 22 locatedopposite the panel 58 coaxially aligned with the bore 66 of the diebutton 62 as shown in FIG. 3. The plunger 60 is then actuated to drivethe free end 28 of the barrel portion 22 against the panel and therelatively sharp cutting or piercing edge 30 of the barrel portion 22cooperates with the relatively sharp cutting or piercing edge 70 of thedie button to pierce a slug 72 from the panel, as shown in FIG. 4. AV-shaped spanking lip 68 then deforms the panel portion 74 into theV-shaped groove 40 in the flange portion 24 and the outer annularbearing surface 38 is driven against the first panel 58 as shown in FIG.4. In the most preferred embodiment of the method of this invention, thecutting edge 70 of the die button simultaneously deforms an annular rib76 radially outwardly from the radial shoulder 36 of the barrel portionshown in FIGS. 1 to 3. The annular radial rib 76 is driven against thedeformed portion 74 of the first panel, entrapping the panel in thegroove 40 and forming a mechanical interlock between the first panel 58and the fastener 20. The spanking lip 68 of the die button 62 furtherdeforms a shallow V-shaped annular recess 78 in the first panel whichreceives the second panel, as described below. Further, the enlargeddiameter portion 34 of the barrel portion is driven through the piercedpanel opening, providing an interference fit, further improving thepull-out strength of the fastener from the first panel assembly.

As described above, it is preferable particularly in mass productionapplications, to securely retain the fastener to the first panel, priorto receipt of the second panel, as described below. In a typical massproduction application, the fastener 20 may be attached to the firstpanel 58 at one station and the second panel may be attached to theassembly at a later station. The first panel and fastener assembly maybe loaded in bins, for example, subjecting the assembly to pull-out andvibrational forces. Further, as described above, the fastener and panelassembly of this invention preferably provides an intimate mattingcontact between the panels and the fastener may be subject tosubstantial torque during attachment of a further element to the panelassembly, as described below. Thus, the fastener and first panelassembly is preferably mechanically interlocked to provide a secureinstallation prior to receipt of the second panel. In a typicalapplication, the push-out strength of the fastener 20 in the first panelformed by the method of this invention is 8 Kn or greater. Further, theradial ribs 42 are driven into the panel portion 74 as the enlargeddiameter portion 34 of the barrel portion is driven into the panelopening, providing excellent torque resistance for the panel assembly.The first panel 58 and fastener assembly is now ready for receipt of thesecond panel, as described below.

The second panel 80 is prepierced for receipt of the barrel portion 22and is preferably deformed adjacent the opening to form a conical lipsurrounding the opening, which may be formed by the apparatus shown inFIGS. 5 and 6. The upper die platen 82 is attached to the upper die shoe84 of the die press by conventional means. The lower die platen 86includes a die member or die button 88 and a plunger 90 is attached tothe upper die shoe by plate or bracket 91. The upper die platen includesa bore 92 which receives the plunger and an annular resilient bumper orbushing 94 is retained in a counter-bore in the bore 92. The die button88 includes a central bore 96 which receives the plunger 90 and a diecavity 98 which forms the panel, as described below. The upper die shoeis spring biased by coil springs 100, normally separating the upper dieplaten 82 from the die shoe 84. When the upper die shoe 84 is lowered bythe die press, the plunger 90 pierces a slug 102 from the panel, asshown in FIG. 6. Continued downward movement of the upper die shoe 84compresses spring 100, which drives the resilient plastic bushing 94against the surface of the panel surrounding the pierced opening,deforming the panel into a generally conical lip 104, as best shown inFIGS. 6 and 7. The conical lip 104 extends from the plane of the panel80 and includes an annular lip 106 spaced from the plane of the panel80. The resilient bumper 94 forms the panel into the desired shape inthe die cavity 98, as best shown in FIG. 6. Further, details of thisoperation are disclosed in the above-referenced copending application.The second panel 80 is now ready for installation on the first panel andfastener assembly formed by the method disclosed in FIGS. 3 and 4, asdescribed below in regard to FIGS. 8 and 9.

The installation apparatus includes an annular plunger 110 which isdriven against the driven surface 56 of the flange portion 24 in aninstallation head (not shown). As described above in regard to theinstallation apparatus for installing the fastener in the first panel58, the installation apparatus may be located in a conventional diepress, such that the second panel 80 is attached to the fastener, witheach stroke of the press. A die button 112 is located in the lower dieplaten which includes a central die post 114 configured to be receivedin the opening 110 formed in the second panel 80 as described above.FIG. 8 is an exploded view of the assembly for illustrational purposes.In a normal application, the panel 80 will be located on the uppersurface 120 of the die button and retained by the stripper plate of thedie press. The die post 114 includes a concave arcuate surface 116 whichblends into the radial outer surface 118 of the die post.

As shown in FIG. 8, the second panel 80 is located in the die press withthe annular edge 106 of the conical portion 104 of the second panel 80facing the first panel 58. The opening 110 is configured to receive thebarrel portion 22. When the plunger 110 is driven downwardly in FIG. 8,as shown by arrows 122, the internal surface 46 of the barrel portion isreceived against the concave surface 116 of the die post, deforming thefree end 28 of the barrel portion radially outwardly over the edge 104of the second panel 80. The panel is simultaneously flattened betweenthe upper surface 120 of the die member and the first panel 58, whichdeforms the conical lip 104 radially inwardly against the outer surfaceof the barrel portion and into the V-shaped recess in the first panel.The second panel 80 is thus deformed against the first panel 58, formingan intimate matting face-to-face contact between the panels and the freeend of the barrel portion is deformed radially outwardly into an arcuatehook-shape over the edge of the second panel surrounding the secondpanel opening in intimate matting contact, forming a secure mechanicalinterlock between the barrel portion 22 and the second panel 80. Theresultant fastener and panel assembly has excellent push-through,pull-out and torque resistance. The push-out strength of the panelassembly is about 15 Kn or greater than about 3,000 lbs. The torqueresistance in a typical application is about 120 newton meters.

FIGS. 10 and 11 illustrate a typical application of the fastener andpanel assembly of this invention. Two fasteners 20 are installed in abracket assembly 124 which comprises panels 58 and 80 by the method andapparatus described above. Both fasteners may be installed in the panels58 and 80 simultaneously in a die press, as described. The disclosedbracket assembly 124 may be attached to a vehicle frame (not shown), forexample, and a structural element 128, such as an axle assembly, is thenattached to the bracket assembly by bolts 130. As shown in FIG. 11, thethreaded portion 132 of the bolt is received in the threaded bore 44 ofthe fastener 20 and the head 134 is driven against the structuralelement 128, securely retaining the structural element 128 to thebracket assembly 124. In a typical application, the bolt is driven intothe nut fastener 20 by a torque wrench, subjecting the nut tosubstantial torque, particularly if the bolt is cross-threaded. Thus,substantial torque resistance of the fastener is required in manyapplications. In the most preferred embodiment, the free end 28 of thebarrel portion is substantially flush with the second panel 80. Furthertightening of the bolt 130, thus, actually requalifies the fastener andpanel assembly by further deforming the free end of the barrel portionagainst the panel assembly. Further, as described above, the panels arein intimate face-to-face contact, preventing any debris from enteringbetween the panels. Finally, the fastener and panel assembly hasexcellent torque resistance, push-through and pull-out resistance,providing a very secure assembly, particularly for applications subjectto vibrational and other forces.

FIGS. 12 and 13 illustrate a method of simultaneously piercing anddeforming a plurality of panels 150 and 152 in nested relation. Thepanels 150 and 152 are supported on an annular surface 156 of a diemember 154 having an annular die cavity 158 and a central bore 160 whichreceives the pierced panel slugs 162 and 164, respectively. The male diemember 166 includes an arcuate conical lip 168 which deforms the panelportions 170 and 172 into the annular die cavity 158 as the punch 174 isdriven against the panels, piercing the panel slugs 162 and 164 and:forming an arcuate panel opening 178, as shown in FIG. 13. The panelportion 150 is deformed into an arcuate generally frustoconical lip 170which blends into the conical lip 172 of panel 152. As described above,the panels 150 and 152 may be retained in face-to-face relation prior topiercing and forming, such as by spot welding, not shown. Further, thepanels may first be pierced in a flat die, then deformed into thepreferred nested frusto-conical shape as shown in FIG. 13 in two steps.Finally, as described above in regard to FIG. 10, a plurality of formedopenings in the panels 150 and 152 may be formed for receipt of aplurality of fasteners 20. The nested panels 150 and 152 are now readyfor attachment to the first panel and fastener assembly as shown in FIG.14.

As described above in regard to FIGS. 8 and 9, the first panel 58 mayfirst be attached to the fastener 20 as described above in regard toFIGS. 3 and 4. The panels 150 and 152 are then reversed from theposition shown in FIG. 13, such that the frusto-conical portions 170 and172 bear against the first panel 58, and the annular plunger 110 is thendriven against the flange portion 24 in an installation head (notshown), which may be located in a die press. The die button 112 includesa central die post 114 which is configured to receive the free end 28 ofthe barrel portion, deforming the barrel portion 28 radially outwardlyagainst the concave surface 116 of the die post. The frusto-conical lips170 and 172 of the panels 150 and 152, respectively, then are flattenedby driving the panels against the first panel 58, driving the lipsradially inwardly against the outer surface of the barrel portion andthe panel 150 is deformed into the generally V-shaped recess 78 in thefirst panel, as described above. Thus, the method of this invention maybe used to attach a plurality of panels to the fastener 20 as describedherein. Finally, in certain applications, it may be desirable to attachfastener 20 directly to the panels 150 and 152, which are first piercedand formed as described above in regard to FIGS. 12 and 13; that is, theassembly may not include a first panel 58.

As will be understood by those skilled in the art, various modificationsmay be made to the fastener and panel assembly and method of thisinvention within the purview of the appended claims. For example, asdescribed above, the fastener may be a male fastener having a threadedor unthreaded shank extending from the flange portion 24 at 26. Further,the fastener may be a more conventional nut fastener, rather than theenclosed nut fastener disclosed, by removing the tubular portion 48. Theinstallation apparatuses disclosed herein are for illustrationalpurposes only and other apparatus may be utilized to install thefastener and form the fastener and panel assembly by the method of thisinvention. Further, although the fastener is preferably installed in adie press, the fastener may be installed upwardly, wherein the diebuttons are located in the upper die shoe or die platen. Finally, asdescribed above, the fastener and panel assembly may include three ormore panels which may require extending the barrel portion 22 of thefastener. Where the "second" panel comprises two or more panels, thepanels are preferably formed with an upstanding generally conical lip104, as described above in regard to FIGS. 12 and 13. The panels maythen be nested and installed simultaneously or sequentially. Havingdescribed the panel assembly and method of this invention, theinventions are now claimed, as set forth below.

I claim:
 1. A method of riveting a plurality of plastically deformablepanels together in face-to-face relation and simultaneously attaching afastener to said panels for attachment of a further element to saidpanels, said fastener including a tubular riveting barrel portion, aflange portion extending radially from adjacent said barrel portionhaving a diameter greater than said tubular barrel portion and afastener portion generally opposite said barrel portion, said methodcomprising the following steps:(a) locating said fastener opposite afirst panel with a free end of said barrel portion facing said firstpanel; (b) driving said fastener barrel portion free end against saidfirst panel and piercing an opening in said first panel; (c) drivingsaid fastener barrel portion through said first panel pierced opening toreceive said flange portion against a top surface of said first paneland securing said fastener to said first panel; (d) forming an openingin a second panel configured to receive said fastener barrel portion;(e) then locating said second panel a bottom surface of on said firstpanel in face-to-face relation with said fastener barrel portionextending substantially through said second panel opening; and (f)deforming said fastener barrel portion radially outwardly to securelyrivet said second panel to said first panel and mechanically affix saidfastener to said panels with said fastener portion extending from saidfirst panel for attachment of said further element to said panels. 2.The method defined in claim 1, wherein said method includes deforming anouter surface of said barrel portion spaced from said free end radiallyoutwardly and against said first panel to form a mechanical interlockbetween said barrel portion and said first panel preventing pull-out ofsaid fastener from said pierced opening prior to receipt of said secondpanel.
 3. The method defined in claim 2, wherein said fastener tubularbarrel portion has a first outside diameter adjacent said free end whichis less then a second outside diameter adjacent said flange portiondefining a generally radial shoulder on said barrel portion and saidmethod including deforming said radial shoulder toward said flangeportion and radially outwardly as defined in claim
 2. 4. The methoddefined in claim 1, wherein said method includes deforming said secondpanel adjacent said opening and forming a generally conical lipsurrounding said second panel opening having a free edge spaced from theplane of said second panel, then locating said second panel on saidfirst panel with said free edge of said second panel engaging said firstpanel.
 5. The method defined in claim 4, wherein said fastener flangeportion includes an annular groove surrounding said barrel portion andsaid method including deforming said first panel adjacent said piercedpanel opening in said flange portion annular groove forming a mechanicalinterlock between said first panel and said fastener.
 6. The methoddefined in claim 5, wherein said fastener annular groove includes aplurality of radial ribs bridging said groove and said method includingdeforming said first panel into said annular groove around said ribspreventing rotation of said fastener in said first panel.
 7. The methoddefined in claim 5, wherein said method includes deforming said firstpanel in said flange portion annular groove forming an annular recess insaid first panel, then locating said second panel on said first panelwith said lip free edge located in said first panel annular recess. 8.The method defined in claim 7, wherein said method includes deformingsaid second panel substantially flat against said first panel, therebydeforming said conical lip radially inwardly against said fastenerbarrel portion as said barrel portion free end is deformed radiallyoutwardly against said second panel, forming a secure mechanicalinterlock between said barrel portion free end and said second panel. 9.The method defined in claim 1, wherein said barrel portion free end hasan outer piercing edge and said method including driving said barrelportion free end against said first panel to pierce a slug from saidpanel having an inside diameter generally equal to said barrel portionfree end.
 10. The method defined in claim 9, wherein said barrel portionfree end has a first diameter adjacent to said barrel portion free endsmaller than a second diameter adjacent said flange portion and saidmethod including driving said barrel through said first panel piercedopening to receive said larger second diameter in said pierced panelopening, retaining said fastener in said first panel opening.
 11. Themethod defined in claim 10, wherein said larger second diameter of saidbarrel portion defines a generally radial shoulder and said methodincluding deforming said shoulder toward said flange portion andradially outwardly over said first panel adjacent said first panelopening securely retaining said fastener on said first panel.
 12. Amethod of permanently attaching a fastener to a plurality of plasticallydeformable panels and simultaneously securing said panels together inface-to-face relation, said fastener including a tubular piercing andriveting barrel portion, a flange portion extending radially fromadjacent said barrel portion having a diameter greater than said barrelportion and a fastener portion generally opposite said barrel portion,said method comprising the following steps:(a) locating said fasteneropposite a first panel with a free end of said barrel portion facingsaid panel; (b) driving said fastener barrel portion free end againstsaid first panel, said barrel portion free end piercing a slug from saidfirst panel and forming an opening in said first panel; (c) driving saidfastener barrel portion through said first panel pierced opening, toreceive said flange portion against a top surface of said first panel,and forming a mechanical interlock between said fastener and said firstpanel; (d) forming an opening in a second panel configured to receivesaid fastener barrel portion; (e) then locating said second panel abottom surface of on said first panel in face-to-face relation with saidfastener barrel portion extending substantially through said secondpanel opening; and (f) deforming said fastener barrel portion radiallyoutwardly over said second panel to securely rivet said first panel andmechanically interlock said fastener to said second panel with saidfastener portion extending from said first panel to attach said furtherelement to said panels.
 13. The method defined in claim 12, wherein saidfastener flange portion includes an annular recess surrounding saidbarrel portion and said method includes deforming said first paneladjacent said pierced panel opening into an annular groove located insaid flange portion forming a mechanical interlock between said firstpanel and said fastener.
 14. The method defined in claim 13, whereinsaid method includes deforming an outer surface of said barrel portionspaced from said free end radially outwardly over said first panellocated in said flange portion radial groove to form said mechanicalinterlock between said barrel portion and said first panel preventingpull-out of said fastener prior to receipt of said second panel.
 15. Themethod defined in claim 14, wherein said barrel portion includes a firstoutside diameter adjacent said free end which is less than a secondoutside diameter adjacent said flange portion defining a generallyradial shoulder and said method including deforming said radial shoulderradially outwardly as defined in claim
 14. 16. The method defined inclaim 12, wherein said method includes deforming said second paneladjacent said opening forming a generally conical lip surrounding saidsecond panel opening having a free edge spaced from the plane of saidsecond panel, then locating said second panel on said first panel withsaid free edge of said second panel engaging said first panel, thenflattening said lip to deform said second panel adjacent said openingradially inwardly against said barrel portion.
 17. The method defined inclaim 16, wherein said fastener flange portion includes an annularrecess surrounding said barrel portion and said method includesdeforming said first panel portion adjacent said pierced panel openingin said annular recess forming a mechanical interlock between said firstpanel and said fastener and an annular recess in said first panelopposite said flange portion, then locating said second panel on saidfirst panel with said conical lip of said second panel located in saidannular recess in said first panel, then flattening said second panel asdefined in claim
 16. 18. The method defined in claim 12, wherein saidbarrel portion free end has a first diameter smaller than a seconddiameter adjacent said flange portion and said barrel portion free endhas an outer piercing edge, said method including driving said barrelportion free end against said first panel to pierce a slug from saidpanel having a diameter generally equal to said barrel portion free endfirst diameter, then driving said barrel portion through said firstpanel pierced panel opening to receive said barrel portion larger seconddiameter in said pierced panel opening, retaining said fastener in saidfirst panel opening.
 19. The method defined in claim 18, wherein saidbarrel portion larger second diameter defines a generally radialshoulder, and said method includes deforming said shoulder radiallyoutwardly over said first panel adjacent said first panel opening,retaining said fastener on said panel.
 20. A method of permanentlyattaching a fastener to a plurality of plastically deformable panels andsimultaneously riveting the panels together in face-to-face relation,said fastener including a tubular barrel portion, a flange portionextending radially from adjacent said barrel portion having a diametergreater than said barrel portion and a fastener portion generallyopposite said barrel portion, and said flange portion including anannular recess generally surrounding said barrel portion adjacent saidbarrel portion, said method comprising the following steps:(a) locatingsaid fastener opposite a first panel with a free end of said barrelportion facing said first panel; (b) forming an opening in said firstpanel configured to receive said barrel portion and driving saidfastener barrel portion through said first panel opening to receive saidflange portion against a top surface of said first panel; (c) thendeforming a portion of said first panel adjacent said first panelopening into said flange portion recess securing said fastener on saidfirst panel; (d) forming an opening in a second panel configured toreceive said fastener barrel portion and deforming a portion of saidsecond panel adjacent second panel opening forming a generally conicallip engaging said first panel; and (f) then deforming said fastenerbarrel portion radially outwardly and substantially simultaneouslydeforming said conical lip of said second panel against said first panelradially inwardly to securely rivet said second panel to said firstpanel and mechanically lock said fastener to said panels with saidfastener portion extending from said first panel for attachment of afurther element to said panels.
 21. The method defined in claim 20,wherein said method includes deforming, an outer surface of said barrelportion spaced from said free end radially outwardly and against saidfirst panel to form a mechanical interlock between said barrel portionand said first panel preventing pull-out of said fastener prior toreceipt of said second panel.
 22. The method defined in claim 21,wherein said fastener barrel portion has a first outside diameteradjacent said free end which is less than a second outside diameteradjacent said flange portion defining a generally radial shoulder andsaid method including deforming said radial shoulder toward said flangeportion and radially outwardly against said first panel to form saidmechanical interlock.
 23. The method defined in claim 20, wherein saidmethod includes deforming said first panel in said flange recess to forman annular recess surrounding said fastener barrel portion in said firstpanel, then locating said first panel on said second panel with saidconical lip bearing against said first panel, then deforming said secondpanel against said first panel, flattening said annular lip of saidsecond panel against said barrel portion and improving the mechanicalinterlock between said second panel and said barrel portion.
 24. Themethod defined in claim 20, wherein said barrel portion free end has anouter piercing edge and said method including driving said barrelportion free end against said first panel to pierce a slug from saidfirst panel having a diameter generally equal to said barrel portionfree end, forming said first panel opening, then driving said barrelportion free end through said first panel opening.
 25. The methoddefined in claim 24, wherein said barrel portion free end has a firstouter diameter smaller than a second outer diameter adjacent said flangeportion and said method including driving said barrel portion throughsaid first panel pierced opening to receive said larger second outerdiameter in said pierce panel opening, further retaining said fasteneron said first panel, prior to receipt of said second panel.
 26. Themethod defined in claim 25, wherein said larger second diameter of saidbarrel portion defines a generally radial shoulder and said methodincluding deforming said shoulder radially outwardly over said firstpanel adjacent said first panel opening, further retaining said fasteneron said first panel.
 27. A method of attaching a fastener to a pluralityof plastically deformable metal panels, said fastener including atubular barrel portion having a free end, a flange portion adjacent saidbarrel portion extending radially generally perpendicular to said barrelportion and a fastener portion generally opposite said barrel portion,said method comprising:(a) locating said plurality of panels inface-to-face relation; (b) piercing an opening in said plurality ofpanels with a punch and deforming a portion of said panels adjacent saidopening to form nested upstanding generally frusto-conical lips in saidpanels having an inside diameter generally equal to an outside surfaceof said barrel portion; (c) receiving said fastener barrel portionthrough said opening in said plurality of panels with said nestedfrusto-conical lips of said plurality of panels facing said fastenerflange portion; and (d) flattening said frusto-conical lips of saidplurality of panels, driving said lips of said plurality of panelsagainst said barrel portion outside surface and substantiallysimultaneously deforming said barrel portion free end radially outwardlyover the adjacent panel, forming a mechanical interlock between saidfastener and said plurality of panels.
 28. The method defined in claim27, wherein said method further includes, prior to the step (c),locating said fastener opposite a first panel with said barrel portionfree end facing said panel, forming an opening in said first panelconfigured to receive said barrel portion and driving said fastenerbarrel portion through said first panel opening, receiving said flangeportion against said first panel and forming a mechanical interlockbetween said fastener barrel portion and said panel, then receiving saidfastener barrel portion through said plurality of panels with saidnested upstanding generally frusto-conical lips facing said first panel,then driving said plurality of panels against said first panel,flattening said frusto-conical lips and driving said panel lips againstsaid barrel portion outside surface as defined in claim
 27. 29. Themethod defined in claim 28, wherein said method includes driving saidbarrel portion free end against said first panel, piercing said openingin said first panel and driving said barrel portion through said piercedfirst panel opening.
 30. The method defined in claim 29, wherein saidfastener barrel portion includes a groove adjacent said barrel portionsurrounding said barrel portion, said method including deforming saidfirst panel in said flange groove, forming said mechanical interlockbetween said fastener and said first panel.